Exercise 1 solution

T = 14 s.
Speed c = 1.56 x 14 = about 21.8 m/s (roughly 79 km/h).
Wavelength L = 1.56 x 14 x 14 = about 306 m.

Check: the deep-water rule applies when depth exceeds L/2 = about 153 m. In 3,000 m of water it does. (Near the shore, where the depth falls below about 150 m, the wave starts to feel the bottom and the rule no longer holds.)